Radiotherapy For Spinal Metastases Research Articles

Comprehensive Review of the Utility of Dynamic Contrast-Enhanced MRI for the Diagnosis and Treatment Assessment of Spinal Benign and Malignant Osseous Disease.

Conventional MRI is currently the preferred imaging technique for detection and evaluation of malignant spinal lesions. However, this technique is limited in its ability to assess tumor viability. Unlike conventional MRI, dynamic contrast-enhanced (DCE) MRI provides insight into the physiologic and hemodynamic characteristics of malignant spinal tumors and has been utilized in different types of spinal diseases. DCE has been shown to be especially useful in the cancer setting; specifically, DCE can discriminate between malignant and benign vertebral compression fractures as well as between atypical hemangiomas and metastases. DCE has also been shown to differentiate between different types of metastases. Furthermore, DCE can be useful in the assessment of radiation therapy for spinal metastases, including the prediction of tumor recurrence. This review considers data analysis methods utilized in prior studies of DCE-MRI data acquisition and clinical implications.

14 A Machine Learning Tool for Prediction of Vertebral Compression Fracture Following Stereotactic Body Radiation Therapy for Spinal Metastases

14 A Machine Learning Tool for Prediction of Vertebral Compression Fracture Following Stereotactic Body Radiation Therapy for Spinal Metastases

T1-Weighted, Dynamic Contrast-Enhanced MR Perfusion Imaging Can Differentiate between Treatment Success and Failure in Spine Metastases Undergoing Radiation Therapy.

Current imaging techniques have difficulty differentiating treatment success and failure in spinal metastases undergoing radiation therapy. This study investigated the correlation between changes in dynamic contrast-enhanced MR imaging perfusion parameters and clinical outcomes following radiation therapy for spinal metastases. We hypothesized that perfusion parameters will outperform traditional size measurements in discriminating treatment success and failure. This retrospective study included 49 patients (mean age, 63 [SD, 13] years; 29 men) with metastatic lesions treated with radiation therapy who underwent dynamic contrast-enhanced MR imaging. The median time between radiation therapy and follow-up dynamic contrast-enhanced MR imaging was 62 days. We divided patients into 2 groups: clinical success (n = 38) and failure (n = 11). Failure was defined as PET recurrence (n = 5), biopsy-proved (n = 1) recurrence, or an increase in tumor size (n = 7), while their absence defined clinical success. A Mann-Whitney U test was performed to assess differences between groups. The reduction in plasma volume was greater in the success group than in the failure group (-57.3% versus +88.2%, respectively; P < .001). When we assessed the success of treatment, the sensitivity of plasma volume was 91% (10 of 11; 95% CI, 82%-97%) and the specificity was 87% (33 of 38; 95% CI, 73%-94%). The sensitivity of size measurements was 82% (9 of 11; 95% CI, 67%-90%) and the specificity was 47% (18 of 38; 95% CI, 37%-67%). The specificity of plasma volume was higher than that of conventional size measurements, suggesting that dynamic contrast-enhanced MR imaging is a powerful tool to discriminate between treatment success and failure.

Introducing the New Patient Expectations in Spine Oncology Questionnaire.

It has been hypothesized that a discrepancy between pretreatment expectations and perceived outcomes is a significant source of patient dissatisfaction. Currently, there is lack in understanding and tools to assess patient expectations regarding the outcomes of treatment for spinal metastases. The objective of this study was therefore to develop a patient expectations questionnaire regarding the outcomes after surgery and/or radiotherapy for spinal metastases. A multiphase international qualitative study was conducted. Phase 1 of the study included semistructured interviews with patients and relatives to understand their expectations of the outcomes of treatment. In addition, physicians were interviewed about their communication practices with patients regarding treatment and expected outcomes. In phase 2, items were developed based on the results of the interviews in phase 1. In phase 3, patients were interviewed to validate the content and language of the questionnaire. Selection of the final items was based on feedback from patients regarding content, language, and relevance. In phase 1, 24 patients and 22 physicians were included. A total of 34 items were developed for the preliminary questionnaire. After phase 3, a total of 22 items were retained for the final version of the questionnaire. The questionnaire is divided into 3 sections: (1) patient expectations regarding treatment outcomes, (2) prognosis, and (3) consultation with the physician. The items cover expectations related to pain, analgesia requirements, daily and physical function, overall quality of life, life expectancy, and information provided by the physician. The new Patient Expectations in Spine Oncology questionnaire was developed to evaluate patient expectations regarding the outcomes after treatment for spinal metastases. The Patient Expectations in Spine Oncology questionnaire will allow physicians to systematically assess patient expectations of planned treatment and thus help guide patients toward realistic expectations of treatment outcome.

Radiotherapy concepts for spinal metastases-results from an online survey among radiation oncologists of the German Society for Radiation Oncology.

Spinal metastases (SM) are acommon radiotherapy (RT) indication. There is limited levelIdata to drive decision making regarding dose regimen (DR) and target volume definition (TVD). We aim to depict the patterns of care for RT of SM among German Society for Radiation Oncology (DEGRO) members. An online survey on conventional RT and Stereotactic Body Radiation Therapy (SBRT) for SM, distributed via e‑mail to all DEGRO members, was completed by 80radiation oncologists between February24 and April29, 2022. Participation was voluntary and anonymous. Avariety of DR was frequently used for conventional RT (primary: n = 15, adjuvant: n = 14). 30 Gy/10 fractions was reported most frequently. TVD in adjuvant RT was heterogenous, with atrend towards larger volumes. SBRT was offered in 65% (primary) and 21% (adjuvant) of participants' institutions. Avariety of DR was reported (primary: n = 40, adjuvant: n = 27), most commonly 27 Gy/3 fractions and 30 Gy/5 fractions. 59% followed International Consensus Guidelines (ICG) for TVD. We provide arepresentative depiction of RT practice for SM among DEGRO members. DR and TVD are heterogeneous. SBRT is not comprehensively practiced, especially in the adjuvant setting. Further research is needed to provide asolid data basis for detailed recommendations.

Stereotactic Body Radiation Therapy for Spinal Metastases: Benefits and Limitations

Progress in biological cancer characterization, targeted systemic therapies and multimodality treatment strategies have shifted the goals of radiotherapy for spinal metastases from short-term palliation to long-term symptom control and prevention of compilations. This article gives an overview of the spine stereotactic body radiotherapy (SBRT) methodology and clinical results of SBRT in cancer patients with painful vertebral metastases, metastatic spinal cord compression, oligometastatic disease and in a reirradiation situation. Outcomes after dose-intensified SBRT are compared with results of conventional radiotherapy and patient selection criteria will be discussed. Though rates of severe toxicity after spinal SBRT are low, strategies to minimize the risk of vertebral compression fracture, radiation induced myelopathy, plexopathy and myositis are summarized, to optimize the use of SBRT in multidisciplinary management of vertebral metastases.

Vertebral body collapse after radiotherapy for spinal metastases.

Spinal metastases are common in patients with advanced stages of cancer and frequently cause vertebral body collapse (VBC). Although conventional radiotherapy (RT) is used for spinal metastases, the rates of occurrence of new VBC and progression of VBC at RT initiation have not been fully investigated. The present retrospective study assessed VBC and its associated risk factors after RT over time and evaluated new VBC and progression of VBC in patients who presented with VBC at RT initiation. The study evaluated 177 patients who received RT for vertebral metastases without paralysis between July 2012 and November 2016. Radiological responses of the irradiated vertebrae were assessed using computed tomography. Follow-up assessments were performed at RT initiation and 1, 2, 3, 4 and 6 months after RT. New VBC occurred in 12% of patients with no prior VBC within 1 month of RT. Multivariate analysis revealed that numeric rating scale (NRS) score (≥4) [relative risk (RR), 27.1; 95% confidence interval (CI), 1.86 to 394.9; P=0.016] was associated with the occurrence of new VBC at the 1 month follow-up time point. VBC progression occurred in 51% of the patients with collapse at RT initiation. Multivariate analysis revealed that bone quality (lytic metastases) (RR, 3.1; 95% CI, 1.28 to 7.70; P=0.013), NRS score (≥4) (RR, 3.0; 95% CI, 1.18 to 7.45; P=0.021) and tumor involvement of posterolateral elements of the spine (RR, 2.7; 95% CI, 1.03 to 7.29; P=0.04) were associated with the progression of VBC at the 1 month follow-up time point. The current study findings suggested that clinicians should pay attention to the factors that predict the occurrence of new VBC and VBC progression to ensure proper evaluation of conservative treatment effectiveness and facilitate the determination of patients who need close monitoring.

Cost-Utility Analysis Compared Between Radiotherapy Alone and Combined Surgery and Radiotherapy for Symptomatic Spinal Metastases in Thailand.

ObjectiveTo investigate the patient quality of life and cost-utility compared between radiotherapy alone and combined surgery and radiotherapy for spinal metastasis (SM) in Thailand. MethodsPatients with SM with an indication for surgery during 2018–2020 were prospectively recruited. Patients were assigned to either the combination surgery and radiotherapy group or the radiotherapy alone group. Quality of life was assessed by EuroQol-5D-5L (EQ-5D-5L) questionnaire, and relevant healthcare costs were collected pretreatment, and at 3-month and 6-month posttreatment. Total lifetime cost and quality-adjusted life-years (QALYs) were estimated for each group. ResultsTwenty-four SM patients (18 females, 6 males) were included. Of those, 12 patients underwent combination treatment, and 12 underwent radiotherapy alone. At 6-month posttreatment, 10 patients in the surgery group, and 11 patients in the nonsurgery group remained alive for a survival rate of 83.3% and 91.7%, retrospectively. At 6-month posttreatment, the mean utility in the combination treatment group was significantly better than in the radiotherapy alone group (0.804 ± 0.264 vs. 0.518 ± 0.282, respectively; p = 0.011). Total lifetime costs were 59,863.14 United States dollar (USD) in the combination treatment group and 24,526.97 USD in the radiation-only group. The incremental cost-effectiveness ratio using 6-month follow-up data was 57,074.01 USD per QALY gained. ConclusionSurgical treatment combined with radiotherapy to treat SM significantly improved patient quality of life compared to radiotherapy alone during the 6-month posttreatment period. However, combination treatment was found not to be cost-effective compared to radiotherapy alone for SM at the Thailand willingness-to-pay threshold of 5,113 USD/QALY.

PO-1141 Stereotactic ablative body radiation therapy for spinal metastases; A single institution study

PO-1141 Stereotactic ablative body radiation therapy for spinal metastases; A single institution study

The Effect of High-Dose Radiation Therapy on Healthy Vertebral Bone Density

ObjectiveIncreased rates of insufficiency fractures are reported after radiation therapy without well-defined causality. Here, we conduct a cross-sectional study on the density change of a non-lesioned vertebral bone after irradiation relative to a control bone in patients with spinal metastases.MethodsPatients were identified who received radiation therapy for spinal metastases to a region, including an adjacent vertebra without identifiable malignancy on pre-treatment CT. Every patient had an untreated vertebra of a similar type available as a control. A Hounsfield-density calibration curve was used to measure the vertebral body density before and after treatment. Analysis of covariance was used to model vertebral bone density changes with respect to treatment status. Significance was established as p < 0.05.ResultsWe identified 36 patients who fit the study criteria. The irradiated healthy bone received a median dose of 30 Gy. The median biologically effective dose (BED) was 60 Gy (α/β = 3) and 39 Gy (α/β = 10). Median follow-up imaging intervals between pre-treatment and follow-up CT scans was 13.4 months. Levene’s test was used to confirm the equality of error variance assumption of ANCOVA (p = 0.093). The mean change in the density of the irradiated vertebral bone was -3.59% (95% CI = -8.51% - 1.32%, p = 0.149).ConclusionsWe found no significant change in vertebral bone density attributable to radiation treatment. Further work is needed to elucidate if increased fracture rates after radiation are due to factors other than bone density.

Radiomic modeling to predict risk of vertebral compression fracture after stereotactic body radiation therapy for spinal metastases.

In the treatment of spinal metastases with stereotactic body radiation therapy (SBRT), vertebral compression fracture (VCF) is a common and potentially morbid complication. Better methods to identify patients at high risk of radiation-induced VCF are needed to evaluate prophylactic measures. Radiomic features from pretreatment imaging may be employed to more accurately predict VCF. The objective of this study was to develop and evaluate a machine learning model based on clinical characteristics and radiomic features from pretreatment imaging to predict the risk of VCF after SBRT for spinal metastases. Vertebral levels C2 through L5 containing metastases treated with SBRT were included if they were naive to prior surgery or radiation therapy, target delineation was based on consensus guidelines, and 1-year follow-up data were available. Clinical features, including characteristics of the patient, disease, and treatment, were obtained from chart review. Radiomic features were extracted from the planning target volume (PTV) on pretreatment CT and T1-weighted MRI. Clinical and radiomic features selected by least absolute shrinkage and selection operator (LASSO) regression were included in random forest classification models, which were trained to predict VCF within 1 year after SBRT. Model performance was assessed with leave-one-out cross-validation. Within 1 year after SBRT, 15 of 95 vertebral levels included in the analysis demonstrated new or progressive VCF. Selected clinical features included BMI, performance status, total prescription dose, dose to 99% of the PTV, lumbar location, and 2 components of the Spine Instability Neoplastic Score (SINS): lytic tumor character and spinal misalignment. Selected radiomic features included 5 features from CT and 3 features from MRI. The best-performing classification model, derived from a combination of selected clinical and radiomic features, demonstrated a sensitivity of 0.844, specificity of 0.800, and area under the receiver operating characteristic (ROC) curve (AUC) of 0.878. This model was significantly more accurate than alternative models derived from only selected clinical features (AUC = 0.795, p = 0.048) or only components of the SINS (AUC = 0.579, p < 0.0001). In the treatment of spinal metastases with SBRT, a machine learning model incorporating both clinical features and radiomic features from pretreatment imaging predicted VCF at 1 year after SBRT with excellent sensitivity and specificity, outperforming models developed from clinical features or components of the SINS alone. If validated, these findings may allow more judicious selection of patients for prophylactic interventions.

Development and Assessment of a Predictive Score for Vertebral Compression Fracture After Stereotactic Body Radiation Therapy for Spinal Metastases

Vertebral compression fracture (VCF) is a potential adverse effect following treatment with stereotactic body radiation therapy (SBRT) for spinal metastases. To develop and assess a risk stratification model for VCF after SBRT. This retrospective cohort study conducted at a high-volume referral center included 331 patients who had undergone 464 spine SBRT treatments from December 2007 through October 2019. Data analysis was conducted from November 1, 2020, to August 17, 2021. Exclusions included proton therapy, prior surgical intervention, vertebroplasty, or missing data. One and 3 fraction spine SBRT treatments were most commonly delivered. Single-fraction treatments generally involved prescribed doses of 16 to 24 Gy (median, 20 Gy; range, 16-30 Gy) to gross disease compared with multifraction treatment that delivered a median of 30 Gy (range, 21-50 Gy). The VCF and radiography components of the spinal instability neoplastic score were determined by a radiologist. Recursive partitioning analysis was conducted using separate training (70%), internal validation (15%), and test (15%) sets. The log-rank test was the criterion for node splitting. Of the 331 participants, 88 were women (27%), and the mean (IQR) age was 63 (59-72) years. With a median follow-up of 21 months (IQR, 11-39 months), we identified 84 VCFs (18%), including 65 (77%) de novo and 19 (23%) progressive fractures. There was a median of 9 months (IQR, 3-21 months) to developing a VCF. From 15 candidate variables, 6 were identified using the backward selection method, feature importance testing, and a correlation heatmap. Four were selected via recursive partitioning analysis: epidural tumor extension, lumbar location, gross tumor volume of more than 10 cc, and a spinal instability neoplastic score of more than 6. One point was assigned to each variable, and the resulting multivariable Cox model had a concordance of 0.760. The hazard ratio per 1-point increase for VCF was 1.93 (95% CI, 1.62-2.30; P < .001). The cumulative incidence of VCF at 2 years (with death as a competing risk) was 6.7% (95% CI, 4.2%-10.7%) for low-risk (score, 0-1; 273 [58.3%]), 17.0% (95% CI, 10.8%-26.7%) for intermediate-risk (score, 2; 99 [21.3%]), and 35.4% (95% CI, 26.7%-46.9%) for high-risk cases (score, 3-4; 92 [19.8%]) (P < .001). Similar results were observed for freedom from VCF using stratification. The results of this cohort study identify a subgroup of patients with high risk for VCF following treatment with SBRT who may potentially benefit from undergoing prophylactic spinal stabilization or vertebroplasty.

Clinical utility of convolutional neural networks for treatment planning in radiotherapy for spinal metastases.

Spine delineation is essential for high quality radiotherapy treatment planning of spinal metastases. However, manual delineation is time-consuming and prone to interobserver variability. Automatic spine delineation, especially using deep learning, has shown promising results in healthy subjects. We aimed to evaluate the clinical utility of deep learning-based vertebral body delineations for radiotherapy planning purposes. A multi-scale convolutional neural network (CNN) was used for automatic segmentation and labeling. Two approaches were tested: the combined approach using one CNN for both segmentation and labeling, and the sequential approach using separate CNN's for these tasks. Training and internal validation data included 580 vertebrae, external validation data included 202 vertebrae. For quantitative assessment, Dice similarity coefficient (DSC) and Hausdorff distance (HD) were used. Axial slices from external images were presented to radiation oncologists for subjective evaluation. Both approaches performed comparably during the internal validation (DSC: 96.7%, HD: 3.6mm), but the sequential approach proved more robust during the external validation (DSC: 94.5% vs 94.4%, p<0.001, HD: 4.5 vs 7.1mm, p<0.001). Subsequently, subjective evaluation of this sequential approach showed that experienced radiation oncologists could distinguish automatic from human-made contours in 63% of cases. They rated automatic contours clinically acceptable in 77% of cases, compared to 88% of human-made contours. We present a feasible approach for automatic vertebral body delineation using two variants of a multi-scale CNN. This approach generates high quality automatic delineations, which can save time in a clinical radiotherapy workflow.

Stereotactic ablative radiation therapy for spinal metastases: experience at a single Brazilian institution.

This study aims to assess the clinical outcomes of patients with spine metastases who underwent stereotactic ablative radiation therapy (SABR) as part of their treatment. SABR has arisen as a contemporary treatment option for spinal metastasis patients with good prognoses. Between November 2010 and September 2018, Spinal SABR was performed in patients with metastatic disease in different settings: radical (SABR only), postoperative (after decompression and/or fixation surgery), and reirradiation. Local control (LC), pain control, overall survival (OS) and toxicities were reported. Eighty-five patients (corresponding to 96 treatments) with spine metastases were included. The median age was 59 years (range, 23-91). In most SA BR (82.3%, n = 79) was performed as the first local spine treatment, while in 12 settings (12.5%), fixation and/or decompression surgery was performed prior to SABR. Two-year overall survival rate was 74.1%, and median survival was 19 months. The LC rate at 2 years was 72.3%. With regard to pain control, among 67 patients presenting with pain before SA BR, 83.3% had a complete response, 12.1% had a partial response, and 4.6% had progression. Vertebral compression fractures occurred in 10 patients (11.7%), of which 5 cases occurred in the reirradiation setting. Radiculopathy and myelopathy were not observed. No grade III or IV toxicities were seen. This is the first study presenting a Brazilian experience with spinal SA BR, and the results confirm its feasibility and safety. SABR was shown to produce good local and pain control rates with low rates of adverse events.

Combined Radiofrequency Ablation and Balloon Kyphoplasty Following Radiation Therapy for Spinal Metastases and Associated Pain. A Case Report

BACKGROUND: The spine is a common area of metastasis to the bone. Radiation therapy has been the standard treatment for focal metastatic spine tumors, and although it has shown an ability to reduce pain, it is not curative for all patients and can negatively impact a patient’s quality of life. Treating spinal metastatic pain with the use of radiofrequency ablation (RFA) in combination with kyphoplasty has been shown to be safe and effective in the treatment of spinal metastatic pain. We present a case of using balloon kyphoplasty with OsteoCoolTM RFA for treating both spinal metastasis and pain. CASE REPORT: A 65-year-old man with a history of prostate cancer presented with metastasis to the L1 vertebral body and chronic low back pain refractory to multimodal pharmacologic treatment. He previously had radiation therapy for this bone metastasis and was maintained on enzalutamide for prostate cancer with decreasing prostate-specific antigens followed by hematology/oncology. Balloon kyphoplasty with OsteoCool RFA was performed with resolution of the patient’s pain as well as the tumor metastasis. CONCLUSION: To our knowledge, there is no available literature discussing the administration of all the above (i.e., RFA, kyphoplasty/vertebroplasty, radiation) together, the sequence in which they are performed, the benefits and consequences of the treatment sequence, the time to and level of pain relief, and differences in radiation exposure. The results of this case provide a clinical rationale for performing RFA and kyphoplasty prior to radiation treatment, while further studies should be conducted to further elucidate the best administration of this treatment. KEY WORDS: Back pain, bone, cancer, kyphoplasty, metastasis, radiation, radiofrequency ablation, vertebroplasty

Stereotactic Body Radiation Therapy for Spinal Metastases: Tumor Control Probability Analyses and Recommended Reporting Standards

We sought to investigate the tumor control probability (TCP) of spinal metastases treated with stereotactic body radiation therapy (SBRT) in 1 to 5 fractions. PubMed-indexed articles from 1995 to 2018 were eligible for data extraction if they contained SBRT dosimetric details correlated with actuarial 2-year local tumor control rates. Logistic dose-response models of collected data were compared in terms of physical dose and 3-fraction equivalent dose. Data were extracted from 24 articles with 2619 spinal metastases. Physical dose TCP modeling of 2-year local tumor control from the single-fraction data were compared with data from 2 to 5 fractions, resulting in an estimated α/β = 6 Gy, and this was used to pool data. Acknowledging the uncertainty intrinsic to the data extraction and modeling process, the 90% TCP corresponded to 20 Gy in 1 fraction, 28 Gy in 2 fractions, 33 Gy in 3 fractions, and (with extrapolation) 40 Gy in 5 fractions. The estimated TCP for common fractionation schemes was 82% at 18 Gy, 90% for 20 Gy, and 96% for 24 Gy in a single fraction, 82% for 24 Gy in 2 fractions, and 78% for 27 Gy in 3 fractions. Spinal SBRT with the most common fractionation schemes yields 2-year estimates of local control of 82% to 96%. Given the heterogeneity in the tumor control estimates extracted from the literature, with variability in reporting of dosimetry data and the definition of and statistical methods of reporting tumor control, care should be taken interpreting the resultant model-based estimates. Depending on the clinical intent, the improved TCP with higher dose regimens should be weighed against the potential risks for greater toxicity. We encourage future reports to provide full dosimetric data correlated with tumor local control to allow future efforts of modeling pooled data.

Quality Assurance of Bone SBRT

Stereotactic body radiation therapy (SBRT) is a high-precision radiation therapy technique that enables to deliver a high ablative biological dose in 1 to 5 high dose-fractions despite sparing the high dose of adjacent organs at risk. SBRT has emerged as an alternative to conventional radiation therapy for spinal metastases and has been applied to patients with non-spine bone metastases as well. Since bone SBRT is the technique of high biologically effective dose to the local lesion, quality assurance (QA) of the entire treatment process is an essential for performing SBRT. This report provides QA procedures for performing bone SBRT.

Patient outcomes and tumor control in single-fraction versus hypofractionated stereotactic body radiation therapy for spinal metastases.

Stereotactic body radiation therapy (SBRT) offers efficient, noninvasive treatment of spinal neoplasms. Single-fraction (SF) high-dose SBRT has a relatively narrow therapeutic window, while hypofractionated delivery of SBRT may have an improved safety profile with similar efficacy. Because the optimal approach of delivery is unknown, the authors examined whether hypofractionated SBRT improves pain and/or functional outcomes and results in better tumor control compared with SF-SBRT. This is a single-institution retrospective study of adult patients with spinal metastases treated with SF- or three-fraction (3F) SBRT from 2008 to 2019. Demographics and baseline characteristics, radiographic data, and posttreatment outcomes at a minimum follow-up of 3 months are reported. Of the 156 patients included in the study, 70 (44.9%) underwent SF-SBRT (median total dose 1700 cGy) and 86 (55.1%) underwent 3F-SBRT (median total dose 2100 cGy). At baseline, a higher proportion of patients in the 3F-SBRT group had a worse baseline profile, including severity of pain (p < 0.05), average use of pain medication (p < 0.001), and functional scores (p < 0.05) compared with the SF-SBRT cohort. At the 3-month follow-up, the 3F-SBRT cohort experienced a greater frequency of improvement in pain compared with the SF-SBRT group (p < 0.05). Furthermore, patients treated with 3F-SBRT demonstrated a higher frequency of improved Karnofsky Performance Scale (KPS) scores (p < 0.05) compared with those treated with SF-SBRT, with no significant difference in the frequency of improvement in modified Rankin Scale scores. Local tumor control did not differ significantly between the two cohorts. Patients who received spinal 3F-SBRT more frequently achieved significant pain relief and an increased frequency of improvement in KPS compared with those treated with SF-SBRT. Local tumor control was similar in the two groups. Future work is needed to establish the relationship between fractionation schedule and clinical outcomes.

PO-1253: Stereotactic Ablative Radiotherapy for spinal metastases: Experience at a Brazilian Institution

PO-1253: Stereotactic Ablative Radiotherapy for spinal metastases: Experience at a Brazilian Institution

Stereotactic body radiation therapy for spinal metastases: a novel local control stratification by spinal region.

This study evaluated a large cohort of patients treated with stereotactic body radiation therapy for spinal metastases and investigated predictive factors for local control, local progression-free survival (LPFS), overall survival, and pain response between the different spinal regions. The study was undertaken via retrospective review at a single institution. Patients with a tumor metastatic to the spine were included, while patients with benign tumors or primary spinal cord cancers were excluded. Statistical analysis involved univariate analysis, Cox proportional hazards analysis, the Kaplan-Meier method, and machine learning techniques (decision-tree analysis). A total of 165 patients with 190 distinct lesions met all inclusion criteria for the study. Lesions were distributed throughout the cervical (19%), thoracic (43%), lumbar (19%), and sacral (18%) spines. The most common treatment regimen was 24 Gy in 3 fractions (44%). Via the Kaplan-Meier method, the 24-month local control was 80%. Sacral spine lesions demonstrated decreased local control (p = 0.01) and LPFS (p < 0.005) compared with those of the thoracolumbar spine. The cervical spine cases had improved local control (p < 0.005) and LPFS (p < 0.005) compared with the sacral spine and trended toward improvement relative to the thoracolumbar spine. The 36-month local control rates for cervical, thoracolumbar, and sacral tumors were 86%, 73%, and 44%, respectively. Comparably, the 36-month LPFS rates for cervical, thoracolumbar, and sacral tumors were 85%, 67%, and 35%, respectively. A planning target volume (PTV) > 50 cm3 was also predictive of local failure (p = 0.04). Fewer cervical spine cases had disease with PTV > 50 cm3 than the thoracolumbar (p = 5.87 × 10-8) and sacral (p = 3.9 × 10-3) cases. Using decision-tree analysis, the highest-fidelity models for predicting pain-free status and local failure demonstrated the first splits as being cervical and sacral location, respectively. This study presents a novel risk stratification for local failure and LPFS by spinal region. Patients with metastases to the sacral spine may have decreased local control due to increased PTV, especially with a PTV of > 50 cm3. Multidisciplinary care should be emphasized in these patients, and both surgical intervention and radiotherapy should be strongly considered.